The present invention relates to the field of electronic test equipment, and more particularly to the field of test fixtures employed in testing electronic components.
As is known in the art, electronic equipment such as computers, video equipment, test equipment and the like are generally comprised of one or more so called printed circuit boards or modules. Printed circuit boards typically have etched conductive patterns and are used to support and interconnect several electrical components including passive devices and in particular integrated circuits. Typically such components have so called external leads or pins used to connect the component to operative positions of the printed circuit board.
As it is also known, during the manufacture of the electronic equipment, it is often necessary to access an external lead or pin of an electronic component mounted on the printed circuit board (PCB) to find and correct flaws in manufacture or design of the board. Generally, it is necessary to provide access to the electronic component on a lead-by-lead basis in order to probe individual connections of the integrated circuits to the printed circuit board. As it is further known, very large scale integrated circuits are often used in electronic equipment and in general have a very large number of electrical leads or pins making access to VLSI (very large scale integration) devices difficult.
One approach, for example, is to solder a "pigtail" on each lead, allowing the attachment of test leads on any pin on the device. Alternatively, a clip pigtail can be employed to make temporary connections to certain types of devices. Such a fixture is designed to make contact with the leads with a particular type of device, and the fixture physically attaches to the device, held in place by spring pressure.
Another approach to this problem is the use of a "vacuum table" fixture which is designed to allow connection to each pin location on the electronic component supported on the printed circuit board. Such a device is secured to the printed circuit board by developing a vacuum in a space between the printed circuit board and a base portion of the fixture. The fixture provides a connection point on each pin located on the board allowing technicians and engineers to gain access to each component on the printed circuit board.
Still another approach has been to use a test fixture including a resilient body which has an attached resilient seal separated by stiffeners. In operation, this type of fixture is aligned with a pin grid array or a dispersion via pattern protruding through the printed circuit board on the side of the printed circuit board opposite the component. In this approach, a vacuum system provides a pressure differential into a well which forces the fixture on to the printed circuit board and causes the test connectors to make contact with the component pins or dispersion vias on the printed circuit board. This approach uses a vacuum type of attachment, which, if not strong enough to hold the test fixture or pod to the printed circuit board, causes a great deal of engineer frustration, inefficiency, and damage when the fixture falls off the printed circuit boards being tested. In addition, this vacuum design needs a relatively wide region disposed about the periphery of the bottom of the fixture base for a vacuum gasket. This wide region precludes adjacent test fixtures from being spaced close together. Therefore, this approach sometimes requires undesirable changes in placement of components on the printed circuit board to allow space for a vacuum gasket seal type of test fixture. Moreover, this type of fixture also requires a vacuum pump or other source of vacuum. This further adds to the cost associated with this type of test fixture and makes use of this type of test fixture impractical if testing is performed at a customer site.